The Rocks fell back to .500 and two games behind the Carolina League's Northern Division-leading Nationals with 12 games remaining in the first half of the season.

"It's hard to sweep a team, normally," Rocks manager Darryl Kennedy said, "and you get them six games. But we lost tonight. We've got four more games with them and we still got a chance."

Potomac took the lead in the second inning and never trailed. After Pleffner hit a leadoff double and advanced to third on a groundout, Will Piwnica-Worms lifted a sacrifice fly to left-center field to give the Nats a 1-0 edge.

Pleffner hit a homer to right field for a 2-0 lead in the fourth. He hit another double and was stranded at third in the sixth.

Hunter Dozier's screaming hit to left field drove in Wilmington's first run and cut its deficit to 2-1 with two outs in the bottom of the sixth inning, but had the ball not hopped over the fence for a ground-rule double, the Blue Rocks might have tied the game.

"I'm not disappointed by it at all," Dozier said. "That's just baseball. … That's the way it goes."

Kennedy was ejected for arguing with the umpire.

"You know, just trying to spark something," he said. "A little motivation there. Was looking for a spark."

The attempted rally was made possible by a fielding error, as Terrance Gore reached first when Potomac third baseman Oscar Tejeda bobbled a ground ball. The speedy Gore advanced to third on a single to right by Raul Mondesi, putting runners on the corners. Bubba Starling struck out for what would have been the final out of the inning before Dozier's RBI double.

Nationals righty Brett Brach earned the victory after allowing one unearned run on three hits in six innings. He struck out four.

Jonathan Dziedzic (5-4) took his second consecutive loss after surrendering two runs on four hits and one walk in five innings. He struck out two. Dziedzic threw 84 pitches, and hasn't lasted more than five innings in any of his last four starts.

"Overall it was definitely better than the last couple," Dziedzic said.

The Rocks stranded Cody Stubbs on second base in the seventh inning.

Wilmington also had two on in the eighth, after Starling singled to left and Dozier walked, but Evans popped out to first.

Cam Gallagher worked a two-out walk in the bottom of the ninth, but Daniel Rockett fouled out to the catcher as Nationals closer Robert Benincasa recorded a four-out save.

"We didn't have much offensively," Kennedy said. "Our big threat was there in that [sixth] inning. Dozier's ball barely goes over the fence. If that ball stays in play, it's a tie ballgame 2-2, because Mondesi is scoring. It is what it is."